(AFP) - Cyclone Gabrielle swept away roads, inundated homes and left 225,000 people without power in New Zealand Tuesday, as a national state of emergency was declared.

High winds and driving rain lashed the country's populous North Island, in what Prime Minister Chris Hipkins called the "most significant weather event New Zealand has seen in this century".

"The impact is significant and it is widespread," he said. "The severity and the damage that we are seeing has not been experienced in a generation."

Daylight Tuesday revealed the severity of the disaster: roads eaten away by landslips and collapsed homes buried in mud, silt and a slew of storm detritus.

Falling trees smashed power lines and floodwaters blocked several major roads, leaving communities stranded.

Local media reported some people were forced to swim from their homes to safety. Others waded through stormwaters on foot. Some were forced to shelter in place.

"During the night a huge tree came down in front of our house, just missing my Ute. It blocked the road and we couldn't get out," 53-year-old Whangamata resident Brendon Pugh told AFP.

"It's been scary, I am an ex-coastguard but I have never seen anything like it in 20 years living here," he said.

"The water in our road was up to my shins, then waist deep in places. We were without power from 10:00 pm last night until about 3:00 pm today and we had no internet."

An estimated 2,500 people have been displaced from their homes, but that number looks certain to rise.

More than three-quarters of New Zealand's five million residents live on the North Island, where the brunt of the storm is being felt.

Some areas are still inaccessible by road and without power or telecommunications.

The main road between the capital Wellington and the country's largest city Auckland is closed. New Zealand's three main mobile phone networks said a total of 455 cell sites were offline.

International and domestic flights were grounded, with Air New Zealand alone reporting more than 600 flights cancelled and 35,000 customers affected, although airports are gradually reopening.

The military has been deployed to help with evacuations.

- 'Cascading' crises -

Cyclone Gabrielle formed off the northeastern coast of Australia in the Coral Sea on February 8, before barrelling across the South Pacific.

It bore down on New Zealand's northern coast on Sunday, bringing gusts of 140 kilometres (87 miles) an hour.

In the next 24 hours, coastal communities were doused with 20 centimetres (almost eight inches) of rain and pounded by 11-metre (36-foot) waves.

Many parts of northern New Zealand were already waterlogged when Cyclone Gabrielle hit, having been drenched by record rainfall two weeks ago.

The national MetService said Auckland Airport received 48 percent of its annual average rainfall in just the past 45 days.

Cape Reinga on the northern tip of the North Island recorded 30 consecutive hours of gale-force winds.

Massey University Professor Christine Kenney warned that New Zealand is living in the age of "cascading" natural disasters -- where the impacts of repeated severe weather events build up over time.

"Cascading natural hazard events fuelled by climate change are the new norm for Auckland," she said ahead of Tuesday's emergency.

Climate scientist Daithi Stone said Cyclone Gabrielle had been feeding off unusually warm seas, driven by a combination of climate change and La Nina weather patterns.

"Gabrielle is very much part of the story this summer of a warm nearby ocean using a warm atmosphere to pump rain onto Aotearoa," he said Tuesday, using the Maori-language name for New Zealand.

"It is also part of the global story of tropical cyclones becoming more intense under human-induced climate change."

"The emergency services are working night and day, but the unstable ground, floodwaters and closed roads are making things hard," said Minister for Emergency Management Kieran McAnulty.

Fire and Emergency New Zealand said one firefighter was injured and another disappeared when a house collapsed west of Auckland. A search is underway.

© Agence France-Presse